Data communications by wireless LAN such as IEEE802.11 are now widely used. Wireless data communications are conducted, for instance, in personal computers (PCs), PC peripherals such as printers, hard disk drives and broadband rooters, electronic apparatuses such as facsimiles, refrigerators, standard-definition televisions (SDTVs), high-definition televisions (HDTVs), digital cameras, digital video cameras and mobile phones, signal-transmitting means in automobiles and aircrafts, etc. In addition to single-band communications, multiband communications have been finding wider applications.
A high-frequency circuit for multiband communications apparatuses using wireless LAN comprises one antenna capable of conducting transmission and reception in two communications systems (IEEE802.11a and IEEE802.11b, and/or IEEE802.11g) having different communications frequency bands, and a high-frequency switch for switching the connection of a transmission circuit and a reception circuit. With wireless apparatuses becoming smaller with higher functions, high-frequency devices have come to have more integrated functions.
WO 2006/003959 discloses a high-frequency device comprising a high-frequency circuit commonly usable for two communications systems, which comprises switch circuits, power amplifier circuits, etc. This high-frequency device is miniaturized by mounting high-frequency-signal-treating circuits such as switch circuits, power amplifier circuits, etc. on a laminate substrate, but it has been found that higher integration makes electrode patterns closer to each other in the laminate substrate, causing interference. For instance, because electrode patterns connected to transmission ports, reception ports, power supply ports, etc. on the rear surface are formed on pluralities of layers, their interference are likely to occur by miniaturization. Particularly when the number of high-frequency-signal-treating circuits such as switch circuits increases, many power supply lines for their control, etc. exist between signal lines, causing much interference.